1. Description of the Prior Art
Many different constructions of valves are known in the art. These valves usually include an inlet for fluid, an outlet for directing the fluid to a desired work application, and a return for collecting the fluid for reuse when the work application has been terminated. Some means are provided internally of the valve for opening and closing fluid flow through the valve.
Such valves, especially when used in high pressure systems, are often damaged by the frequent and severe movement of the metal pieces back and forth against each other over an extended period of time and by shock waves inherent in closing of valves in high pressure systems.
One of the shortcomings with known valves for use in high pressure systems where leakage can be a problem is the requirement that they be demounted from an existing piping structure in the event of damage to or failure of the valve. The inconvenience and attendant damage to the surrounding piping structure is a major drawback to valve replacement. Leaks can occur during re-piping and the system, in that case, would be required to be shut down again to fix the leak.
Another shortcoming is that valves employed in high pressure hydraulic applications tend to require considerable mechanical input in order to actuate the valve from a first to a second position because of the high seal pressure and related high friction forces necessary to insure sealing. This often results in the necessity of increasing the output of an attendant air source beyond what is convenient for the application.
Another problem associated with known valves is that contaminants affect the seal life so severely that especially where chips and the like can find their way into the hydraulic system the life of the valves can be very short.
Still another problem is that in conventional high pressure valves high sealing forces are required to insure a dead tight seal.